In general, SOI(silicon-on-insulator) wafer which is an essential device widely used in various electronic instruments, control systems and communication equipments, has a structure of thin single crystalline silicon film which plays a role as active area on insulating layer consisting of thin insulating film such as silica.
FIG. 1 shows a schematic diagram of the conventional SOI wafer which has a structure consisting of single crystalline silicon wafer(1), thin insulating film(2) positioned on the silicon wafer(1), and thin single crystalline silicon film(3) on the insulating film(2).
A variety of technologies for the manufacture of the conventional SOI wafer have been reported in the art:
Frey, R. C. et al. disclose a process for preparing SOI wafer by employing wafer bonding method which comprises the steps of contacting two silicon wafers having oxidized membrane of silica each other by facing both sides having the silica membrane or contacting one side having the said silica membrane, bonding them by heat treatment and forming thin silicon film by the aid of polishing and chemical etching of the other side of slicon wafer(see: Frey, R. C. et al., J. Elecetrochem. Soc., 133:1673(1986)).
Lam, H. W. describes a process for preparing SOI wafer by SIMOX(separation by implanted oxygen) method which comprises implanting oxygen ion of high energy into a silicon wafer to form an oxidized layer implanted on the silicon wafer(see: Lam, H. W., IEEE Circuits and Dev. Mag., 3(4):6-11(1987)).
Further, Fan, J. C. C. et al. teach a ZMR(zone melting recrystallization) technique which comprises the steps of partial heating of thin amorphous or polycrystalline silicon film on thin insulating membrane such as silica to form molten zone on the membrane, and producing a thin silicon film which is solidified to the moving direction of energy source to grow single crystalline silicon(see: Fan, J. C. C. et al., J. Crystal Growth, 63:453-483(1983)).
However, the said prior art processes are proven to be less satisfactory in the sense that they are complex, and provide low degree of crystallization of the thin single crystalline silicon film as active area of SOI wafer due to the use of thin insulating membrane, which, in turn, produce a limited size of SOI wafer only, and in which gettering process to remove defects or contaminants of SOI wafer can not be readily employed.
Under the circumstances, there are strong reasons for exploring and developing a novel process for preparing a, large-sized SOI wafer in a simple and efficient manner.